Why USDC is not safe?

I've been hearing some concerns about the safety of USDC. Could you please explain why some people believe it's not secure? I've noticed that it's supposed to be a stablecoin, backed by the US dollar, but I'm still uncertain about its reliability. Are there any specific risks associated with USDC that investors should be aware of? Also, how does it compare to other stablecoins in terms of safety? I'd like to get a better understanding of its underlying mechanisms and any potential vulnerabilities it may have.